White Board: Relative Dating

Here's a whiteboard drawing from today's lesson on the fossil record.  The slide for the topic of relative dating wasn't that good, so I drew this on the fly.

Here, using relative dating, we can determine that the T-Rex skull is older than the human skull but younger than the trilobite.

Bean Counters: A Rabbit Breeding Simulation

To simulate genetic shift in a population, we'll be breeding rabbits.  But, because the gestation period for a rabbit spans longer than the two 57-minute periods allotted for this lab, we had to settle for a simulation to squeeze in 10 generations.  Instead of rabbits, we'll be using red and white beans to simulate dominant and recessive alleles.

W. E. Castle discovered an English breed of rabbits that sometimes produce furless offspring.  England is cold.  Not having fur is usually a death sentence for our hoppy friends.  But it does give us a good model for testing out genetic shift over generations.

The lab setup:

1. In a cup (our Gene Pool), there are 100 beans.  50 are red, representing the dominant allele (normal fur - H) and 50 that are white, representing the recessive allele (furless rabbit - h).
2. Students will randomly pull two beans from our gene pool.
3. HH combinations and Hh combinations will "survive" and be placed back in a cup for the next generation.
4. hh combinations will be eliminated from the gene pool.
5. Students will record the number of remaining H and h beans in the gene pool and move on to the next generation.

Over the 10 generations, the white beans should be quickly reduced but not eliminated.  This lab has a bunch of moving parts and will require some clear instruction, but it should go well.

Here's a shot of the whiteboard.

Hardy-Weinberg - Math Meets Biology

I heard a science teacher say that all biologists think they're chemists, all chemists think they're mathematicians, and all mathematicians think they're God.  Well, today in Honors Biology, we skipped over the chemists and went straight for math.  Though, after a day of wrestling with their first exposure to solving Hardy-Weinberg equations, only a few students felt like deity.

Here's a shot of the whiteboard.

I also had my first observation by my college supervisor.  He came 4th period, so I had a chance to practice beforehand.  Overall, the observation went well.  There were a few items related to small classroom management strategies that I need to improve.  The timing of handing out worksheets was one of the issues mentioned.  I began the lesson and forgot to hand out the papers during a down period when students were solving a bit of math.  Overall it didn't hurt the entire lesson, but it did create an awkward lag in the lesson as I hurriedly passed out papers.  His second suggestion was that I not turn my back to the class when I write on the board.  This one may take a while to fix; I already have trouble writing on a whiteboard while facing the board directly.  Changing my stance may degrade my whiteboard-manship.  But, it'll be important to learn this skill so I'll work on it.

Tomorrow we'll finish up the Hardy-Weinberg equations and watch a short clip of genetic drift in action.

Crabby Graphs

A lot has happened since my days in science class.  Even in college, we used peppered moths as the example of natural selection.  Peppered moths have been hammered into our minds.  I rather like our peppered moth friends, but it's also nice to mix things up.

Enter pocket mice and freshwater crabs.  Like the peppered moths, both pocket mice and freshwater crabs demonstrate natural selection in their coloration.  Last week, we used pocket mice as the last activity to solidify the concepts of natural selection; this week we will add data to the concept of natural selection as we look at populations of freshwater crabs.

Today's activity will revolve around specific types of selection in relation to environmental changes of freshwater crabs.  We will cover directional selection, disruptive selection, and stabilizing selection.  Towards the end of the period the students will be looking at data and will be graphing  phenotype frequencies (light to dark coloration) to determine the type of selection in a specific scenario.

Today's Goal:  Students will understand the concepts of directional selection, disruptive selection, and stabilizing selection.  Given phenotype frequency over time, students will be able to graph data and determine the type of selection for a given scenario.

Here's a shot of the whiteboard:

Today's Whiteboards: Why You Can't Roll Your Tongue

Some people can roll their tongues into a taco shape.  Others can't.  Some people are pretty tall.  Others are short.  Today's lesson will cover some of the reasons for these alleles.

After a short activity on the evolution of the pocket mouse, we're going to begin chapter 16: Evolution of Populations.

I've got a nifty PowerPoint, but I've also got my powers of whiteboard wizardry.  Below is a snapshot of the whiteboard I'll be using to teach Single Gene Traits (tongue rolling) and Polygenic Traits (height).